The increasing number of frequency bands and standards in mobile communication systems increases the design complexity of mobile phones, as some mobile phones are now configured to operate using multiple standards across multiple frequency bands. In addition, the mobile phone may also include a Global Positioning System (GPS) receiver. In many mobile phones, these multiple frequency bands and standards are implemented by using multiple radio frequency (RF) transmitters and receivers within multiple signal paths that may be coupled to a single antenna using an antenna switch. The introduction of more and more frequency bands within the mobile phone, however, may cause some issues with respect to jamming due to the creation of distortion products within circuitry of the mobile phone and within the antenna switch itself.
In mobile phone systems that have multiple antennas, distortion products created in the transmitter may leak into the receive path via one of the multiple antennas or via parasitic paths within the mobile phone itself. An example of this is the case of the mobile phone that has an antenna used to communicate with a base station according to one of the various mobile telecommunication standards, and GPS receiver. If, for example, one of the mobile phone transceivers is a Universal Mobile Telecommunications System (UMTS) transceiver operating on band 13 with uplink frequencies in the range of 777 MHz to 787 MHz, second order distortion products may be generated within the GPS frequency band at about 1572 MHz. Some conventional mobile phone systems may address this issue by using a costly and bulky Hi-Q sharp band stop filter in series with the antenna port, because the GPS band is only about 150 MHz away from several cellular telephone bands.